It is the long term industry vision to base wireless and wireline networks on MMTel/IMS architecture in the future. It is obvious that this migration step will take a long time and that “legacy” services (e.g. SMS) need to be supported. Some known solutions provide a migration path from MSS towards IMS by reusing the existing MSC-S as application server. At present, there is an ongoing debate about which mechanism to select to provide SMS over LTE radio access. In the following, known available alternatives for SMS over LTE are summarized.
OMA-IM is specified in CNA-TS-Simple IM series of specifications and in 3GPP TS 24.247. It supports deferred messaging over IMS and can support text messaging capabilities with a similar user experience to user-to-user text messaging using SMS and also can support similar capabilities as those provided by MMS. Support for domain selection is defined in specification 23.204.
Another known technique is typically referred as SMS over IP, as specified in 3GPP 23.204. All existing SMS capabilities are supported through SMS encapsulation in IP.
A further known technique is known as SMS in CS Fallback, specified in 3GPP 23.272. SMS is carried in NAS signalling when camping on LTE; operator can configure network and terminal to use SMS over IP instead. This requires CS Fallback capable phones and networks and also requires CS/PS mode 1 or mode 2 of operation (3GPP TS 24.301). It is noted that CS Fallback is seen as interim step before introducing MMTel over LTE, but not necessarily used together with MMTel “just” to provide SMS plus IP telephony.
A further known technique is known as GAN, which is under study in 3GPP TR 23.879 and in VOLGA. It provides all CS services in LTE, including SMS, over PS bearer. The current status is that the GAN based solution will not be adopted by 3GPP as a number of operators objected to it.
A further known technique is known as SMS in PS. SMS over PS access is specified for GPRS access, but not for EPS.
FIG. 6 represents some details of the known technique of SMS over IP 23.204. FIG. 6 shows the architecture of SMS over IP as defined in TS 23.204. It is apparent that the IP-SMS-GW is defined as an application server attached via ISC to the IMS core nodes. After registration in the IMS, the subscriber can send and receive SMS. An example of handling of subscriber initiated SMS is illustrated in FIG. 7. FIG. 8 illustrates an example of handling of subscriber initiated Instant Message (IM).
The sequence as such is very similar for SMS and IM, however, the format of the text message differs (SMS versus IM format).
Further as background information, reference is made to ICSI (IMS Communication Service Identities). An IMS Communication Service Identifier (ICSI) provides a framework for the identification of IMS communication services utilizing the IMS enablers. An IMS communication service is provided via the use of the IMS enablers. At terminals, the use of a communication service identifier is similar to the use of the port concept in TCP/IP, in that it allows applications in a terminal and the network that use SIP for communication purposes to be identified. In the terminal this means dispatching a SIP message to the correct application, and in the network it means selection of the correct application server over ISC. Examples of IMS based applications and communication services are MMTel, OMA messaging and OMA PoC.
One problem with the known techniques is that there is no clear solution for providing SMS in LTE. One problem with the known techniques as for instance outlined above is that additional efforts for system integration are needed. In the known techniques, furthermore, a redesign or adaptation of the applications, services or functionalities is needed in order to support legacy services in new generation networks. The present invention is, amongst others, based on this recognition of the inventors, namely that a solution is required for providing EMS in LTE reusing existing functionalities and minimizing efforts for system integration while avoiding redesign or redevelopment of applications and services.